I recently bought a fender bassman 135 and in the process also traded my GK backline 600 for it which was 4 ohms. I still have the cab that came with it (Backline 410 BLX-II), and i kinda assumed it was also 4 ohms. But its 8 ohms. its loud, but im wondering if i get an actually 4 ohm 4x10 cab will it crank alot more?
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Bassman 135 questions
- Thread starter insane bass
- Start date
depends on what you mean by alot.
I'd say not. It won't double the perceived volume, but it will make the amp work as close to optimally as possible.
Good way to go with those heads (which are really more like 100w, as has been discussed here frequently) is to get 2 very efficient 8ohm cabs for a total 4 ohm load. This will at least make the most of the watts you have to work with, and push some air in the process.
good luck
It works that way with solid state powered amps but tube powered amps typically achieved the same maximum power levels at all ohm levels they're designed to operate at. Your 8 ohm cab should be just as loud as an otherwise identical 4 ohm cab with your Bassman 135 .
I would plan on getting a 4 ohm cab or adding a second 8 ohm cab. There's a bit of controversy on here about whether it's safe to use 8 ohm cabs with tube heads that have 4 ohm output transformers. I used an SVT head with a 4 ohm transformer with an 8 ohm cab tonight on my gig, and it did no damage to it (it was a rental so it's OK), but some say it will damage the amp. Regardless, everyone seems to agree that tube heads sound better if you match the cab to the transformer.
Whether you want to add a second cab or buy a whole new one is up to you and how much you want to carry, but either will work.
Whether you want to add a second cab or buy a whole new one is up to you and how much you want to carry, but either will work.
Ah nostalgia. I had a Bassman 135 30 years ago. Seems a bit underpowered these days, but I found mine was OK to keep up with a drummer.
Davo
Davo
Hi,
the bassman 135 could operate at 4 or 8 Ohm with a single cab or with 2x4 Ohm cabs. The Bassman 135 has an output transformer with 4 or 8 Ohm. You can plug a 4 Ohm cab into the speaker output (that's for 4Ohm) The 8 Ohm output is the ext. Speaker. here you can plug a single 8 Ohm cab. If you want to use 2 cabs there must both be 4 Ohm. Plug them into speaker and ext. speaker. The internal circut will automatically connect the cabs in series.
I you can read schematics, i have attached the output section of the bassman 135 as you will find the schematics on the net.
Bye willie
the bassman 135 could operate at 4 or 8 Ohm with a single cab or with 2x4 Ohm cabs. The Bassman 135 has an output transformer with 4 or 8 Ohm. You can plug a 4 Ohm cab into the speaker output (that's for 4Ohm) The 8 Ohm output is the ext. Speaker. here you can plug a single 8 Ohm cab. If you want to use 2 cabs there must both be 4 Ohm. Plug them into speaker and ext. speaker. The internal circut will automatically connect the cabs in series.
I you can read schematics, i have attached the output section of the bassman 135 as you will find the schematics on the net.
Bye willie
Attachments
this is incorrect, as applies to the amp in question. at mismatched impedances (either up OR down), the amp will be outputting less than full power--- 25-30% less; there is a way to calculate it exactly, but the formula escapes me. so, into a 2 ohm load OR an 8 ohm load, the amp will output less power than at 4 ohms. the fender amps can deal with the mismatch pretty well, but i wouldnt try that with your JCM800.
Wow this has all been alot of help, thanks! 
Im trying to learn alot about amps, obviously im a nooblet haha.
So Basically what your saying willie, is that if i plug into the ext. speaker i will get full power?
And yeah toobalicious i think i read that if you had a 4 ohm 300w head and pluged it into an 8 ohm cab it would be only getting 200w of juice.
Im trying to learn alot about amps, obviously im a nooblet haha.
So Basically what your saying willie, is that if i plug into the ext. speaker i will get full power?
And yeah toobalicious i think i read that if you had a 4 ohm 300w head and pluged it into an 8 ohm cab it would be only getting 200w of juice.
Yes, if your cab is running at 8 ohm.Wow this has all been alot of help, thanks!
Im trying to learn alot about amps, obviously im a nooblet haha.
So Basically what your saying willie, is that if i plug into the ext. speaker i will get full power?
...
But you have a head with 135W. So if you plugin the 8 Ohm cab in the 4 Ohm (Speaker) output, you will get round about 100W on the fender. (I have measured it with an 8 Ohm cab (EV 12L))
Our second guitarist has a 16 Ohm engl cab working on this amp on the normal output (4Ohm). I think there was only 50 or 60 w and it sounds awful. After switching the output to external speaker, the sound was better, but not good and not loud enough. What i want to say is, that especially on tube amps it is very important to work on the right impedanz. Not for the output power but for the sound, too.
Yeah i have a Backline 4x10BLX-II Gallien krueger cab (kinda crappy). It runs at 8 ohms, so now i guess im hoping it will sound much better and louder on the ext. speaker. Thanks much willie.
eh thats about all really wanted, already it sounded louder than my other head. Other head was alot lower quality, Gallien Krueger Backline 600, things EQ didnt even do anything!
i think i like tubes alot better haha
i think i like tubes alot better haha
No. You are incorrect. The Bassman 135 has 4 or 8 ohm taps on its output transformer, both of which, deliver full power. So to the OP, there is no power advantage to a single 4 ohm cab, however, adding another 8 ohm cab will increase the acoustic output. Also, if you mismatch impedance upwards in a tube amp, you get MORE than rated power, but at the expense of stability.
One of my first amps was a bassman 135, had a bassman 100 before that. If it hasnt been serviced in a while, it might be a good idea to invest in a cap job.
also the ugly blue and brown caps inside the amp could be changed out too. Guitar guys would recommend Orange Drops but I would go for Solens, those are used in the kern bass preamp wich is a fnacy black face fender anyways.
also the ugly blue and brown caps inside the amp could be changed out too. Guitar guys would recommend Orange Drops but I would go for Solens, those are used in the kern bass preamp wich is a fnacy black face fender anyways.
Just got a Bassman 135 as well. Powering an Ampeg SVT410HLF...no volume or power problems. The 410HLF is 4 ohm
I see two jacks and they are both 4 ohm (not one at 4 and one at 8) When you plug a second speaker of 4 ohms into the extension jack then the impedance would be 2 ohms. I have never heard of plugging a speaker into the extension jack without a plug inserted in the main jack first. Where are you seeing 8 ohms in your schematic?
hmm... was not aware that 135 had multi-tap OT--- some assuming was done on my part. bassman 100 definitely does NOT. seems interesting that fender would do that, since the "bassman 135" cab is a 4 ohm 4x12.
so each jack is connected to a different tap, and they wired in series? i am no EE, and never claim to be, but this doesnt seem right?
every pre-80's fender amp *i* have seen for more than a fleeting moment (which certainly isnt all of them) had a single tap OT, and the jacks were wired in parallel, but with a switching jack on the "main" one--- the ext jack would not work unless something was inserted into the main jack.
but yes, multi-tap OT nullifies my earlier post.
That's OK; I remembered the tap values wrong. They're both 4 ohms according to the skit. I could swear the last Bassman 135 I saw had an 8 ohm main out and 4 ohm extension labelled on its jacks, but that's been quite a few years ago.
They're not hooked up in series. There is a switching jack in the extension like the SVT.
This one has two taps, a green wire and green/yellow wire feed off the output transformer.
